They tested so-called lamb dishes, and were shocked to discover four of the curries contained none whatsoever.

Instead they featured a mixture of pork, beef or chicken – all cheaper cuts of meat, leaving consumers both duped and ripped off, said officers.

The findings would also cause concern for people who would unwittingly find themselves eating meats they are prohibited from consuming due to their religious beliefs or health issues, officers added.

Incredibly, none of the 20 lamb kebabs sampled contained just lamb – instead they were all made up of lamb mixed together with either pork, beef or chicken.

Of the 19 lamb curries tested, only three contained just lamb. Again, most contained a mixture of lamb together with either beef or chicken.

The products were also tested by Warwickshire County Council’s Trading Standards for artificial colourings, which can trigger health problems such as cancer, allergies, and asthma in adults, as well as hyperactivity and behavioural issues in children.

Seventy per cent of the kebabs tested contained high levels of artificial colourings – one was 18 times higher than the legal limit and another was 13 times over the permitted levels.

None of the curries had high levels of artificial colourings. In the wake of the study, Birmingham trading standards officers are planning to test outlets across the city.

Coun Richard Hobbs, Warwickshire council’s portfolio holder for community safety, said: “Consumers rely on accurate food descriptions – some foods are not permitted to be eaten by some religions and cultures, whilst some people may wish to avoid some foods because of allergy concerns.

“Consumers should also have the confidence that, if they are buying an expensive product such as lamb, they are not getting chicken instead, a meat that is about half the price.”

He said Trading Standards were now contacting every restaurant and takeaway involved, which can not be named for legal reasons, and they may face prosecution. The eateries are all in areas across Nuneaton, Rugby, Leamington Spa and Stratford-upon-Avon. Investigations continue and no arrests have yet been made.

Nick Lowe, operations manager at Birmingham City Council’s environmental health team, said a similar probe could now take place at Birmingham restaurants and takeaways later this year.

“I am very surprised by the survey findings, certainly we have never come across this issue in routine sampling we have done,” he said.

“I will speak to our laboratory and consider adding this to our sampling programme for this year.”

He said Birmingham’s environmental health and trading standards teams had done extensive work relating to food on sale in the city in a bid to protect consumers.

“In fact we developed a guidance note on the correct use of food colourings in products such as kebabs and curries, but also for Asian style sweets,” he added.

“We have a number of kebab manufacturers in our area and much of our focus has been around ensuring that products are correctly labelled with the meats that they contain.”